Wednesday August 31 2011
It is rare for the virus to spread from birds to humans
The United Nations has this week warned of a possible global resurgence of the bird flu virus, which has been widely covered in the media. News sources, such as the BBC, have also reported the circulation of a mutant strain that is able to “sidestep” current vaccines.
The UN’s Food and Agriculture Organization issued the warning after rises in the numbers of birds infected with the H5N1 strain of avian flu virus. The virus is not readily passed to humans but since it first appeared in 2003 the H5N1 strain has infected 565 people globally, 331 of whom died. However, these people were overwhelmingly individuals farming birds or raising poultry within their own homes. There is also evidence of birds in Vietnam and China becoming infected with a mutant strain that existing vaccines do not offer protection against.
It is important to remember that for people living in the UK the risk of contracting bird flu is extremely low. Although the bird flu virus is still present in other countries, the UK became officially free of bird flu in November 2008. The World Health Organization has pointed out that the evolution of the H5N1 virus poses no increased risk to public health.
What is avian flu?
Within birds, avian influenza, or ‘bird flu’, is a highly infectious virus that can affect species including chickens, ducks, turkeys and geese. The disease can be passed between farmed birds, wild birds and pet birds. Avian flu is spread in birds through bird droppings (which can contaminate soil), water, feed and equipment. The virus can also be carried on the feet and bodies of birds.
The bird flu virus is closely related to human flu viruses and has multiple strains or types, some of which are more dangerous than others. However, the virus does not easily transmit to humans, who generally have to be in very close contact to become infected. In cases where humans have contracted the virus it has often been in individuals farming birds or living with birds inside their homes. However, on the rare occasions that humans have contracted avian flu it has shown an ability to cause severe disease and death, often in previously healthy children and young adults.
The strain of avian flu that has caused concern in recent years is called H5N1. It is often deadly to birds, and has infected numerous species of birds in Asia, Europe and Africa. The strain has forced the culling of more than 400 million domestic poultry since it appeared in 2003.
Why is it in the news again today?
Bird flu is in the news because the UN’s Food and Agriculture Organization (FAO) has issued a warning over a possible major resurgence of H5N1, as well as the circulation of a new mutant strain of the virus.
The UN says that although the virus had been eliminated from most of the 63 countries infected at its peak in 2006, it remained endemic in six countries – Bangladesh, China, Egypt, India, Indonesia and Vietnam. And although the number of outbreaks in domestic poultry and wild birds shrank steadily from an annual peak of 4,000 to just 302 in mid 2008, outbreaks have risen progressively since, with almost 800 cases recorded in 2010–2011.
The UN considers the year 2008 to mark the beginning of “renewed geographic expansion” of the H5N1 virus in both poultry and wild birds, an advance that appears to be associated with migratory bird movements that may allow the virus to be carried over long distances. In the past two years, H5N1 has shown up in poultry and wild birds in countries that had been virus-free for several years. Recently-affected areas include Israel and the Palestinian Territories, Bulgaria, Romania, Nepal and Mongolia.
In Vietnam and China, a new variant of the virus known as H5N1 - 18.104.22.168 has also appeared. This strain, which is now found across most of northern and central Vietnam, can apparently sidestep the defences provided by existing vaccines. The UN says this mutant strain poses a threat to nearby countries such as Cambodia, Thailand and Malaysia, as well as the Korean peninsula and Japan further afield. Wild bird migration can also potentially spread it to birds in other continents.
The World Health Organization has pointed out that the evolution of the H5N1 virus poses no increased risk to public health. It says that human cases of H5N1 infection remain rare and occur mostly in areas where H5N1 viruses circulate regularly in poultry. However, Juan Luborth, the FAO’s chief veterinary officer has said that “preparedness and surveillance remain essential” when dealing with the threat the virus poses to farmed and wild birds, adding that “no one can let their guard down with H5N1”.
How is it spread to people?
The H5N1 virus does not easily infect humans, and since it emerged in 2003 it is only reported to have infected 565 people globally. It can pass directly from poultry to humans as a result of direct contact with infected birds, such as during home slaughter and plucking of infected poultry. Most cases in humans have been the result of prolonged, close contact with infected birds, among people with close associations to poultry, such as those working on chicken farms or raising chickens inside their homes.
At present the virus does not appear to be able to spread readily between humans. However, there is concern that it may undergo genetic changes that enable it to spread easily between humans, possibly by interacting with the human influenza viruses. If this happened, there would be a greater risk to people.
Can it be passed through food?
Avian flu is not transmitted through cooked food. In areas that have experienced outbreaks of bird flu, poultry and eggs can be safely eaten if handled and cooked properly.
Can I travel to affected areas?
If you are travelling in a country that has had avian flu outbreaks, do not go to live animal markets or poultry farms. Avoid bird droppings or dead birds and do not bring any live birds or poultry products back with you, including items containing feathers.
Do I need to take other precautions?
The risk to anyone in the UK of contracting H5N1 is extremely low, although people who work with or handle poultry are at slightly higher risk. People in this group are entitled to an annual flu vaccination. Although the current flu vaccines do not protect against avian flu, protecting against human flu reduces the risk of the viruses mixing.
You can feed wild birds and ducks but always wash your hands thoroughly afterwards and do not go near sick or dead birds. Keep away from bird droppings and wash your hands thoroughly if you accidentally touch some.
There is generally no need to change the way you look after pets, although if you have a dog that sometimes catches wild birds try to avoid areas where this is likely. In theory, H5N1 can be passed on to other animals but it is very unlikely.
It is always important to practise good hygiene, such as washing hands regularly and handling meat correctly, to prevent the spread of infection.